Each year, the operation processes millions of pounds of hazardous materials from Utah and around the West, including contaminated soils, pesticides, industrial solvents and out-of-date pharmaceuticals.

The Utah Department of Environmental Quality issued 48 violations against the West Desert facility in 2007 and 2008. Regulators said 10 violations had a "major" potential for harm, including several fires.

As part of the deal, the company will pay $153,000 in cash, build storage facilities for certain kinds of chemicals and install roof-mounted monitors intended to detect potentially explosive contaminants

Scott Anderson, manager of the state's hazardous waste branch, said it's one of the largest hazardous waste settlements ever reached in Utah.

The incinerator _ which has changed hands several times since opening in 1991 _ has a history of trouble with state regulators.

Prior to the latest round of violations, the DEQ had issued more than $644,000 in penalties. That includes $323,666 in fines for 89 violations since Clean Harbors took over in 2002, according to DEQ records.

Company officials said the latest problems came during a time of high turnover at the plant and difficulty in getting new employees up to speed on complicated regulations and procedures.

"We regret that the enforcement actions had to occur but we have learned from them," Phillip Retallick, Clean Harbor's senior vice president of regulatory affairs, said after Thursday's decision.

Since then, new managers have been brought in, employment has stabilized, audits have been conducted and steps have been taken to make sure the operation complies with the law, he said.

"We look forward to showing the state of Utah, and the Utah Department of Environmental Quality, that we have made significant improvements and will continue to make significant improvements," Retallick said.

Clean Harbors calls itself the largest hazardous waste disposal company in North America. The Aragonite facility is one of four incineration operations it runs in the United States.

Many of the violations in Utah involved failures to keep track of shipments, violations of storage regulations and problems with documentation. Among the more serious were several fires at the site, lapses in monitoring for radioactive waste, a lack of monitors checking for dangerous vapors and recorded results for tests that were never conducted.

The settlement, which took months to negotiate, was 40 percent less than it could have been based on per-violation calculations. State officials, in proposing the initial draft, said it had been adjusted downward because of the current economic crisis and a "significant reduction" in the amount of waste coming into the plant.

Of the eight state board members who voted on the settlement Thursday, two dissented, wondering if the penalties were stiff enough.